CN112998648A

CN112998648A - Imaging system

Info

Publication number: CN112998648A
Application number: CN202110142153.XA
Authority: CN
Inventors: 张少林; 吴瑾照; 郭丽丽; 陈梦婕
Original assignee: Shenzhen Wave Kingdom Co ltd
Current assignee: Shenzhen Wave Kingdom Co ltd
Priority date: 2021-02-02
Filing date: 2021-02-02
Publication date: 2021-06-22

Abstract

The application relates to an imaging system, which comprises an acousto-optic crystal, a laser emission device, an ultrasonic emission device and an optical imaging device, wherein the laser emission device and the optical imaging device are respectively arranged at two opposite sides of the acousto-optic crystal; the laser emitting device emits laser to the acousto-optic crystal, the ultrasonic emitting device emits ultrasonic to the acousto-optic crystal, the optical imaging device collects ultrasonic which is emitted into the acousto-optic crystal and a first diffraction light signal generated by Bragg diffraction of the laser, collects ultrasonic which is reflected by a target to be imaged and a second diffraction light signal generated by Bragg diffraction of the laser in the acousto-optic crystal to be imaged, obtains distance information according to time difference of two times of collection and preset ultrasonic propagation speed, and obtains an optical image of the target to be imaged according to the imaged image and the distance information. By adopting the method and the device, the resolution ratio can be improved and no radiation hazard exists.

Description

Imaging system

Technical Field

The present application relates to the field of image inspection technology, and more particularly, to an imaging system.

Background

Clinical medical image testing typically employs non-invasive imaging testing. At present, the common non-invasive imaging detection is generally B-ultrasonic, CT (Computed Tomography), nuclear magnetic resonance, etc.

CT and nuclear magnetic resonance, etc. have radiation; although B-ultrasound has the advantages of nondestructive and radiationless imaging detection of human tissues and organs, the size of the ultrasound transducer array element adopted by B-ultrasound imaging is generally millimeter level, and the large size of the array element directly limits the imaging resolution, so that the spatial resolution of ultrasound imaging is not high.

Disclosure of Invention

In view of the above, there is a need to provide an imaging system that can improve resolution without radiation hazard.

An imaging system, comprising: the device comprises an acousto-optic crystal, a laser emitting device, an ultrasonic emitting device and an optical imaging device, wherein the laser emitting device and the optical imaging device are respectively arranged on two opposite sides of the acousto-optic crystal, and the ultrasonic emitting device and a target to be imaged are respectively arranged on two opposite sides of the acousto-optic crystal;

the laser emitting device emits laser to the acousto-optic crystal, the ultrasonic emitting device emits ultrasonic to the acousto-optic crystal, the optical imaging device collects a first diffraction light signal generated by Bragg diffraction of the laser and the ultrasonic emitted into the acousto-optic crystal, collects a second diffraction light signal generated by Bragg diffraction of the laser in the acousto-optic crystal and the ultrasonic reflected after the acousto-optic crystal reaches the target to be imaged, obtains a time difference for collecting the first diffraction light signal and the second diffraction light signal, obtains distance information according to the time difference and a preset ultrasonic propagation speed, and obtains an optical image of the target to be imaged according to the imaged image and the distance information.

In the imaging system, a laser emitting device and an ultrasonic emitting device are adopted to respectively emit laser and ultrasonic to an acousto-optic crystal, an optical imaging device collects a first diffraction light signal generated by Bragg diffraction of the laser and the ultrasonic, collects a second diffraction light signal generated by Bragg diffraction of the ultrasonic and the laser after the ultrasonic reaches a target to be imaged and returns, and images, distance information is obtained according to the time difference of two times of collection and the preset ultrasonic propagation speed, and an optical image is obtained according to the distance information and the imaged image; by combining ultrasonic detection and laser, the target to be imaged is detected based on the ultrasonic, no radiation hazard exists, information of the target to be imaged, which is obtained by the ultrasonic detection, is transmitted to diffraction light signals through Bragg diffraction, an optical imaging device is adopted for optical imaging, the array element size of the optical imaging is small, and the imaging resolution is high.

In one embodiment, the acousto-optic crystal is made of tellurium dioxide.

In one embodiment, the laser light is at an angle equal to the Bragg diffraction angle with respect to the propagation direction of the ultrasonic wave.

In one embodiment, the imaging system further includes an optical fiber and a laser collimator, the laser collimator is disposed between the laser emitting device and the acousto-optic crystal, and the laser emitting device is connected to the laser collimator through the optical fiber.

In one embodiment, the imaging system further comprises a light homogenizer and a light transmission component with a window, wherein the light homogenizer is arranged between the laser emission device and the acousto-optic crystal, and the light transmission component is arranged between the light homogenizer and the acousto-optic crystal;

the laser emitted by the laser emitting device passes through the light homogenizer and the light transmission component to form a uniform light beam with the size matched with the ultrasonic field formed by the ultrasonic wave, and the uniform light beam is incident to the acousto-optic crystal.

In one embodiment, the window is rectangular.

In one embodiment, the imaging system further includes a beam expanding unit disposed between the laser emitting device and the light homogenizer.

In one embodiment, the beam expanding unit includes a first lens and a second lens with different focal lengths and diameters, and the first lens and the second lens are sequentially disposed between the laser emitting device and the light homogenizer.

In one embodiment, the imaging system further includes a first polarizer disposed between the laser emitting device and the acousto-optic crystal, and a second polarizer disposed between the acousto-optic crystal and the optical imaging device.

In one embodiment, the imaging system further comprises a focusing lens disposed between the acousto-optic crystal and the optical imaging device.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of an imaging system in one embodiment;

fig. 2 is a schematic structural view of an imaging system in another embodiment.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.

It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or be connected to the other element through intervening elements. Further, "connection" in the following embodiments is understood to mean "electrical connection", "communication connection", or the like, if there is a transfer of electrical signals or data between the connected objects.

As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

In one embodiment, referring to fig. 1, there is provided an imaging system comprising: the acousto-optic crystal 110, the laser emitting device 120, the ultrasonic emitting device 130 and the optical imaging device 140, the laser emitting device 120 and the optical imaging device 140 are respectively arranged at two opposite sides of the acousto-optic crystal 110, and the ultrasonic emitting device 130 and the object to be imaged 200 are respectively arranged at two opposite sides of the acousto-optic crystal 110. For example, taking the acousto-optic crystal 110 as a three-dimensional hexahedron as an example, the acousto-optic crystal includes an upper surface, a lower surface, a front surface, a rear surface, a left surface and a right surface, the laser emitting device 120 is disposed on the left side of the acousto-optic crystal 110, the optical imaging device 140 is disposed on the right side of the acousto-optic crystal 110, the ultrasonic emitting device 130 is disposed on the rear side of the acousto-optic crystal 110, and the object to be imaged 200 is disposed on the front side of the acousto-optic crystal 110.

Wherein, the laser emitting device 120 is a device capable of emitting laser, and the ultrasonic emitting device 130 is a device capable of emitting ultrasonic; the acousto-optic crystal 110 is an acousto-optic coupling medium, and when ultrasonic waves pass through the acousto-optic coupling medium, elastic deformation is caused, so that the dielectric coefficient and the refractive index of the acousto-optic coupling medium are changed periodically, which is equivalent to forming a phase grating; at the moment, when laser enters the acousto-optic coupling medium at a certain angle with the ultrasonic propagation direction, the ultrasonic frequency is high, the coherence action length is long, the laser can generate Bragg diffraction in the acousto-optic coupling medium, and a +1 or-1 order diffraction light signal is generated, so that amplitude and phase information carried by the ultrasonic wave is transmitted to the diffraction light signal.

The optical imaging device 140 is a device that can detect optical signals and image them. The laser emitting device 120 emits laser to the acousto-optic crystal 110, the ultrasonic emitting device 130 emits ultrasonic to the acousto-optic crystal 110, the optical imaging device 140 collects the ultrasonic which is emitted into the acousto-optic crystal 110 and a first diffraction light signal which is generated by Bragg diffraction of the laser, collects the ultrasonic which is reflected after the acousto-optic crystal 110 reaches a target to be imaged and a second diffraction light signal which is generated by Bragg diffraction of the laser in the acousto-optic crystal to be imaged, obtains a time difference for collecting the first diffraction light signal and the second diffraction light signal, obtains distance information according to the time difference and a preset ultrasonic propagation speed, and obtains an optical image of the target to be imaged according to the imaged image and the distance information. That is, after the laser emitting device 120 emits laser to the acousto-optic crystal 110 and the ultrasonic emitting device 130 emits ultrasonic to the acousto-optic crystal 110, the laser and the ultrasonic generate Bragg diffraction in the acousto-optic crystal 110 to generate a diffraction light signal as a first diffraction light signal, the ultrasonic passes through the acousto-optic crystal 110 to reach the target 200 to be imaged and then is reflected, and the ultrasonic generates Bragg diffraction with the laser again in the acousto-optic crystal 110 to generate a diffraction light signal as a second diffraction light signal; the optical imaging device 140 collects the first diffraction light signal and the second diffraction light signal, images based on the second diffraction light signal, and acquires a time difference between the collected diffraction light signals. Specifically, the optical imaging device 140 acquires the signals of the two diffracted lights within one pulsed ultrasound cycle.

When the ultrasonic wave is incident to the target 200 to be imaged, for example, the target 200 to be imaged may be a human tissue or an organ, after reaching the target 200 to be imaged, due to the change of the acoustic impedance, the ultrasonic wave is reflected by the surface of the target 200 to be imaged, the reflection degrees caused by different acoustic impedances are different, while the reflection is generated, a part of the ultrasonic wave enters the inside of the target 200 to be imaged and continues to propagate forward, the density structures of different targets are different, the caused attenuation is also different, and the ultrasonic wave continues to propagate forward, when the acoustic impedance changes, the ultrasonic wave is reflected at two different acoustic impedance interfaces, the amplitude change of the ultrasonic echo caused by attenuation and reflection carries the information of the morphology and structure of the target 200 to be imaged, and the propagation time corresponding to the ultrasonic echo carries the distance information of the target. The intensity of the ultrasonic echo is adjusted by the target 200 to be imaged, the intensity distribution of which is directly related to the structure of the object to be imaged, and meanwhile, in Bragg diffraction, the relationship between the ultrasonic intensity and the diffraction efficiency satisfies the following formula:

where M is the quality factor of the acousto-optic crystal 110, n is the refractive index of the acousto-optic crystal 110, ρ is the density of the acousto-optic crystal 110, P is the elastic-optic coefficient of the acousto-optic crystal 110, and V is_SIs the propagation velocity of the ultrasonic waves in the acousto-optic crystal 110; i is₀Is the ultrasonic intensity, P_sThe elastic-optical coefficient of the acousto-optic crystal 110, H, L is the height and length of the acousto-optic crystal 110 respectively; lambda [ alpha ]₀Is the wavelength of the laser, and η is the diffraction efficiency.

As can be seen from the formula, the ultrasound intensity is optically related to the height and length of the acousto-optic crystal 110. The higher the Bragg diffraction efficiency is, the stronger the light intensity of the corresponding diffraction light signal is, that is, the amplitude of the ultrasonic echo is in direct proportion to the acoustic impedance of a certain area due to the large acoustic impedance of the area, that is, the higher the ultrasonic intensity corresponding to the ultrasonic echo is, the higher the Bragg diffraction efficiency is caused, and the stronger the corresponding diffraction light signal is; the transmission of the information carried by the ultrasonic waves is completed through the relation between the ultrasonic intensity and the diffraction efficiency; according to the difference of Bragg diffraction efficiency, the ultrasonic echo intensity carries the shape and structure information of the target 200 to be imaged to transmit to diffraction light signals, and high-resolution optical images can be obtained by collecting the diffraction light signals to carry out imaging and combining distance information. Specifically, the optical imaging device 140 may generate an optical image by obtaining a gray scale value from the diffraction light signal and associating the gray scale value with the distance information.

Taking the target 200 to be imaged as a human tissue and an organ as an example, the human tissue and the organ are scanned by ultrasonic waves, the ultrasonic waves are reflected by the human tissue and the organ, and the wave front of the ultrasonic waves is modulated by the human tissue and the organ, so that the morphology and the structure information of the human tissue and the organ are carried; when the ultrasonic waves reflected by the human tissues and organs return to pass through the acousto-optic crystal 110, an ultrasonic grating is formed in the acousto-optic crystal 110; when passing through the acousto-optic crystal 110 with an ultrasonic field, laser acts with ultrasonic waves in a Bragg diffraction mode under a proper condition to generate a + 1-order or-1-order diffraction light signal, and the appearance and structure information of human tissues and organs carried by the wave front of the ultrasonic waves is transmitted to the + 1-order or-1-order diffraction light signal; because the ultrasonic wave front pattern and the image formed by the diffraction light signal form a one-to-one corresponding relation, the wave front pattern information reflected by the human tissue and the organ can be obtained by collecting the image formed by the diffraction light signal, thereby obtaining the image of the human tissue and the organ.

Specifically, the optical imaging device 140 may record the time when the first diffraction light signal is received and the time when the second diffraction light signal is received, and calculate the time difference between the recorded times. It is understood that the optical imaging device 140 can also obtain the time difference in other manners, such as starting the timing when the first diffraction light signal is received and stopping the timing when the second diffraction light signal is received, so as to obtain the time difference. The distance information refers to a distance from the target 200 to be imaged; the optical imaging device 140 may calculate the distance information by using a preset calculation model.

Taking the recording of the time of two acquisitions as an example, receiving the first diffraction light signal and recording the time to obtain a first time, receiving the second diffraction light signal and recording the time to obtain a second time, and calculating to obtain distance information according to the first time, the second time and the ultrasonic propagation speed, wherein the calculation formula is as follows:

S＝1/2V*(T2-T1)

wherein S is distance information, V is ultrasonic propagation velocity, and T₂Is a second time, T₁Is the first time.

On one hand, considering that the size of an array element in an imaging system can directly influence the lateral resolution of imaging, the size of the array element of an ultrasonic transducer used in the traditional ultrasonic imaging is far larger than that of the array element of the optical imaging device 140, and the lateral resolution of the corresponding ultrasonic imaging is low; the lateral resolution of the imaging can be improved by optically imaging the second diffracted light signal with the optical imaging device 140. On the other hand, since the conventional ultrasonic imaging obtains the distance information of the object 200 to be imaged according to the flight time of the ultrasonic wave, the accuracy of the distance information corresponds to the axial resolution; considering that the corresponding information can be obtained only by receiving a whole envelope in the ultrasonic imaging, the limit value of the axial resolution of the ultrasonic imaging is lambda/2, so that certain errors can be caused in the distance information in the detection process, and the axial resolution of the space can be influenced; in view of this, in the present application, by using the diffracted light signal obtained by the first Bragg diffraction of the ultrasonic wave and the laser as the reference light, and simultaneously obtaining the diffracted light signal obtained by the second Bragg diffraction of the ultrasonic wave and the laser reflected by the object 200 to be imaged, the distance information of the object 200 to be imaged can be accurately obtained by the time difference (flight time) between the reference light and the signal light, and the accuracy of the obtained flight time is higher than that of the ultrasonic transducer used in the conventional ultrasonic imaging, so that the axial resolution of imaging can be improved.

In the imaging system, a laser emitting device 120 and an ultrasonic emitting device 130 are adopted to respectively emit laser and ultrasonic waves to an acousto-optic crystal 110, an optical imaging device 140 collects a first diffraction light signal generated by Bragg diffraction of the laser and the ultrasonic, collects a second diffraction light signal generated by Bragg diffraction of the laser and the ultrasonic after the ultrasonic reaches a target 200 to be imaged and returns, and images, distance information is obtained according to the time difference of two collection and the preset ultrasonic propagation speed, and an optical image is obtained according to the distance information and the imaged image; by combining ultrasonic detection and laser, the target 200 to be imaged is detected based on ultrasonic, no radiation hazard exists, information of the target 200 to be imaged, which is obtained by ultrasonic detection, is transmitted to diffraction light signals through Bragg diffraction, and optical imaging is performed by the optical imaging device 140, so that the array element size of the optical imaging is small, and the imaging resolution is high.

In one embodiment, acousto-optic crystal 110 is an acousto-optic crystal made of tellurium dioxide. The acousto-optic crystal prepared from tellurium dioxide has high quality; by using the acousto-optic crystal with higher quality factor, the Bragg diffraction efficiency can be improved, and meanwhile, the stability of acousto-optic interaction is improved. It is understood that in other embodiments, the acousto-optic crystal 110 can be made of other materials with higher quality factors, such as lithium niobate, lead molybdate, lead bromide, mercurous chloride, etc.

In one embodiment, the laser emitting device 120 is an infrared laser. The infrared laser is a device for emitting infrared laser, and has small divergence angle of infrared laser beams, high brightness and good use effect.

In one embodiment, the ultrasonic wave emitting device 130 may include an excitation signal controller connected to the ultrasonic transducer and an ultrasonic transducer disposed on a side of the acousto-optic crystal 110 opposite to the target 200 to be imaged.

The excitation signal controller sends a pulse signal to the ultrasonic transducer, and the ultrasonic transducer receives the pulse signal and transmits ultrasonic waves to the acousto-optic crystal 110. Specifically, the excitation signal controller may complete the control of the high voltage excitation signal, i.e., the pulse signal, according to the set control parameters. The ultrasonic transducer is controlled to emit ultrasonic waves by adopting the excitation signal controller, and the structure is simple.

In particular, the ultrasonic transducer may be a transducer probe which emits ultrasonic waves at a frequency of 2MHz to 15MHz under the action of a pulse signal, the probe having a relatively good acoustic backing to reduce the number of cycles within a pulse envelope.

In one embodiment, the optical imaging Device 140 includes a CCD (Charge-coupled Device) disposed on the side of the acousto-optic crystal 110 opposite to the laser emitting Device 120. The CCD is adopted for optical imaging, the imaging effect is good, and the resolution ratio is high.

In one embodiment, the laser light is at an angle equal to the Bragg diffraction angle to the propagation direction of the ultrasonic wave. Wherein the Bragg diffraction angle is a predetermined angle. An ultrasonic transducer is used for emitting a beam of pulse ultrasonic wave, the ultrasonic wave is directly coupled into the acousto-optic crystal 110 to cause the refractive index of the acousto-optic crystal 110 to be periodically distributed to generate a phase grating, the included angle between the incident laser and the propagation direction of the ultrasonic wave at the moment meets the Bragg diffraction angle, and the Bragg diffraction angle formula is as follows:

wherein λ is₀Is the wavelength of the laser, f_sIs the ultrasonic frequency, n is the refractive index of the acousto-optic crystal 110, V_sIs the speed of propagation of the ultrasonic waves in the acousto-optic crystal 110.

When the Bragg diffraction angle is satisfied, the ultrasonic frequency is high, and the coherent action length of the ultrasonic wave and the laser is long, the coupling action of the ultrasonic wave and the laser beam in the acousto-optic crystal 110 satisfies the Bragg diffraction condition, and the Bragg diffraction only generates a +1 order or-1 order diffraction light signal.

In one embodiment, referring to fig. 2, the imaging system further includes an optical fiber 151 and a laser collimator 152, the laser collimator 152 is disposed between the laser emitting device 120 and the acousto-optic crystal 110, and the laser emitting device 120 is connected to the laser collimator 152 through the optical fiber 151. The optical fiber 151 conducts laser light to facilitate adjustment of the incident angle of the laser light, and the laser collimator 152 is used for collimating the laser light emitted from the optical fiber 151 into parallel light.

In one embodiment, the imaging system further includes a light homogenizer disposed between the laser emitting device 120 and the acousto-optic crystal 110, and a light transmitting component with a window disposed between the light homogenizer and the acousto-optic crystal 110. The laser emitted by the laser emitting device 120 is integrated into a uniform beam with a size matched with the ultrasonic field formed by the ultrasonic wave through the light homogenizer and the light transmission component, and the uniform beam is incident to the acousto-optic crystal.

The dodging device is used for ensuring that the light intensity of the laser beam incident into the acousto-optic crystal 110 is uniformly distributed; the laser beam passes through the dodging device, so that the light intensity distribution of the cross section of the laser beam is uniform. The light-transmitting component with the window is used for adjusting the size of the laser beam by adopting the window; the laser beam with uniform light field intensity passes through the window, specifically, the size of the window is adjustable, and the shape and the size of the laser beam are adjusted by adjusting the size of the window, so that the size of the laser beam can be adjusted as required, and the laser beam is specifically adjusted to be matched with the ultrasonic sound beam. If the laser beam is too large, the redundant part can act as background noise to influence the imaging of a diffraction light signal, and if the laser beam is too small, a part of ultrasonic echo does not participate in Bragg diffraction to cause the loss of information. Therefore, by adjusting the size of the laser beam, the incident laser is matched with the ultrasonic sound beam, and the imaging precision is improved.

Specifically, as shown in fig. 2, the imaging system includes a light integrator and a light transmissive assembly with a window, which are combined into an integral body 170. The dodging device may be disposed after the laser collimator 152 and before the acousto-optic crystal 110.

In one embodiment, the window is rectangular. Because the interaction length exists in the acousto-optic effect, and the ultrasonic field and the laser beam are vertically acted, if the ultrasonic field is a circular light spot, the diameter and the edge of the circular light beam are uneven when the ultrasonic field passes through the circular light spot, especially when the circular light spot follows Gaussian distribution, the edge intensity is lower, and the diffraction efficiency is positively correlated with the light field intensity. By adopting the rectangular window, the laser emitted by the laser emitting device 120 is changed into the rectangular beam, so that the light field intensity at the edge can be ensured to increase the diffraction efficiency, and meanwhile, the rectangular beam can be better matched with the ultrasonic sound beam.

In one embodiment, the imaging system further includes a beam expanding unit disposed between the laser emitting device 120 and the dodging device. Through expanding the beam unit, expand the diameter of laser beam and expand, specifically, expand the beam unit and expand the diameter of laser beam and reach the aperture consistent with dodging ware, improve dodging effect.

In one embodiment, as shown in fig. 2, the beam expanding unit includes a first lens 161 and a second lens 162 having different focal lengths and diameters, and the first lens 161 and the second lens 162 are sequentially disposed between the laser emitting device 110 and the dodging device. The beam expanding unit is formed by two lenses with different focal lengths and diameters, the first lens 161 diffuses laser, and the second lens collimates the diffused laser, so that the purpose of expanding laser beams is achieved, and emergent laser spots are amplified by proper times.

Specifically, as shown in fig. 2, the first lens 161 and the second lens 162 are sequentially disposed between the laser collimator 152 and the light homogenizer, and the laser emitted by the laser emitting device 120 reaches the laser collimator 152 through the optical fiber 151 and then sequentially passes through the first lens 161, the second lens 162, the light homogenizer and the window of the light transmitting component.

In one embodiment, with continued reference to fig. 2, the imaging system further includes a first polarizer 181 and a second polarizer 182, the first polarizer 181 is disposed between the laser emitting device 120 and the acousto-optic crystal 110, and the second polarizer 182 is disposed between the acousto-optic crystal 110 and the optical imaging device 140.

The light beam emitted by the acousto-optic crystal 110 actually has not only +1 st order or-1 st order diffraction light signals, but also has non-modulated zero order diffraction light, which is the main noise for imaging and can not be filtered by the optical filter because the wavelength is almost consistent with the wavelength of the diffraction light signals; meanwhile, because the included angle between the +1 st order or-1 st order diffraction light signal and the zero-order diffraction light is 2 times of the Bragg diffraction angle, the Bragg diffraction angle is small, and because the light beam has a certain divergence angle, the light beam emitted from the acousto-optic crystal 110 has a small incidence angle, the +1 st order or-1 st order diffraction light signal and the zero-order diffraction light can be mixed together, the +1 st order or-1 st order diffraction light signal and the zero-order diffraction light are difficult to be separated through a traditional diaphragm at a short distance, and the zero-order diffraction light can easily enter the CCD as noise, so that the imaging quality of the +1 st order or-1 st order. When the diffraction efficiency is low, the intensity of the zero-order diffracted light as noise even exceeds the intensity of the +1 or-1 order diffracted light signal, so that the optical image of the target 200 to be imaged cannot be obtained.

The first polaroid 181 is added before the laser enters the acousto-optic crystal 110, and the first polaroid 181 is adopted to polarize the incident laser beam, so that the laser entering the acousto-optic crystal 110 is linearly polarized; a second polarizer 182 is added before the diffracted light signals are emitted and collected into the optical imaging device 140, the second polarizer 182 analyzes polarized incident light, the polarization direction of the second polarizer 182 is required to be perpendicular to the polarization direction of the first polarizer 181, the +1 st order or-1 st order diffracted light is diffracted by the Bragg, the polarization direction of the +1 st order or-1 st order diffracted light is changed to a certain extent, so the +1 st order or-1 st order diffracted light can pass through the second polarizer 182, the zero order diffracted light cannot pass through the second polarizer 182 because the polarization direction of the second polarizer 182 is perpendicular to the first polarizer 181, the filtering effect on the zero order diffracted light is achieved, the +1 st order or-1 st order diffracted light is ensured to enter the optical imaging device 140, the zero order diffracted light is filtered, and the signal-to-noise ratio of Bragg diffraction imaging is improved so as to improve the.

Specifically, as shown in fig. 2, the first polarizer 181 is disposed between the whole 170 of the light homogenizer and the light transmitting component with the window and the acousto-optic crystal 110, and after the laser light is shaped into a rectangular beam by the light homogenizer and the window, the rectangular beam is incident into the acousto-optic crystal 110 through the first polarizer 181.

In one embodiment, as shown in FIG. 2, the imaging system further comprises a focusing lens 190, and the focusing lens 190 is disposed between the acousto-optic crystal 110 and the optical imaging device 140. The focusing lens 190 collects the diffracted light signals and focuses the diffracted light signals into the optical imaging device 140. Specifically, the focusing lens 190 is disposed between the second polarizing plate 182 and the optical imaging device 140.

Taking an infrared laser as an example, and referring to fig. 2 for describing the use of the imaging system in detail, after the infrared laser light source is emitted from the infrared laser, the infrared laser light source passes through the optical fiber 151, the laser collimator 152, the first lens 161, the second lens 162, the light homogenizer, the rectangular window, and the first polarizer 181 in sequence, so as to ensure that the laser beam is uniformly incident into the acousto-optic crystal 110 in a rectangular shape and with a certain polarization direction. The operation comprises the following steps:

s1: laser emitted by an infrared laser is changed into parallel laser beams through an optical fiber 151 and an optical fiber collimator 152, the parallel laser beams sequentially pass through a first lens 161 and a second lens 162 to be expanded, then the laser beams are changed into rectangular laser beams with adjustable sizes through a light homogenizer and a rectangular window, the light intensity distribution of the cross section of the laser beams is uniform, and the rectangular laser beams are changed into the laser beams with certain polarization directions through a first polaroid 181 and are incident into the acousto-optic crystal 110.

S2: the laser emitted from the acousto-optic crystal 110 passes through the second polarizer 182, passes through the focusing lens 190, enters the CCD for imaging, and the second polarizer 182 is adjusted so that the intensity of the laser received by the CCD is at the lowest when no ultrasonic wave passes through the acousto-optic crystal 110.

S3: and starting the ultrasonic transducer to emit pulse ultrasonic waves, and adjusting the directions of the laser beams and the ultrasonic beams to ensure that an included angle between the laser beams and the ultrasonic beams meets Bragg diffraction conditions.

S4: ultrasonic waves emitted by the ultrasonic transducer are transmitted to a target 200 to be imaged, Bragg diffraction is carried out between the ultrasonic waves and rectangular light beams in the acousto-optic crystal 8, due to the Bragg diffraction, emitted laser has zero-order diffraction light signals and + 1-order or-1-order diffraction light signals, the included angle between the two beams is 2 times of Bragg angle, the second polaroid 182 is finely adjusted to enable the light intensity of the + 1-order or-1-order diffraction light signals to be maximum, meanwhile, the minimum intensity of the zero-order diffraction light is guaranteed, and the + 1-order or-1-order diffraction light signals and the acquisition time T1 are recorded through a CCD.

The Bragg diffraction light signal passes through the second polarizing plate 182 having a polarization direction perpendicular to the polarization direction of the first polarizing plate 181, the laser light that is not diffracted cannot pass through the second polarizing plate 182 and is filtered, and the Bragg diffraction light signal passes through the second polarizing plate 182 and enters the CCD.

S5: when the ultrasonic wave reaches the target 200 to be imaged, the reflected ultrasonic wave passes through the acousto-optic crystal 110 again, Bragg diffraction is carried out on the ultrasonic wave, a diffraction light signal is collected by the CCD, and the collection time T2 is recorded.

S6: the surface topography and the image of the structure of the object 200 to be imaged are obtained through CCD imaging, and meanwhile, the axial distance information of the object 200 to be imaged is obtained according to the recorded time T1 and T2 and the ultrasonic propagation speed.

The Bragg diffraction of infrared laser and ultrasonic is used as a basic principle to carry out high-resolution optical imaging on a target to be imaged, the method plays an active role in the field of medical image detection, replaces the traditional ultrasonic imaging detection with the high-resolution imaging, greatly improves the imaging resolution, and reduces the problems of misdiagnosis, missed diagnosis and the like caused by insufficient resolution of B-ultrasonic imaging.

In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. An imaging system, comprising: the device comprises an acousto-optic crystal, a laser emitting device, an ultrasonic emitting device and an optical imaging device, wherein the laser emitting device and the optical imaging device are respectively arranged on two opposite sides of the acousto-optic crystal, and the ultrasonic emitting device and a target to be imaged are respectively arranged on two opposite sides of the acousto-optic crystal;

2. The imaging system of claim 1, wherein the acousto-optic crystal is an acousto-optic crystal made of tellurium dioxide.

3. The imaging system of claim 1, wherein the laser light is angled from a propagation direction of the ultrasonic wave by an angle equal to a Bragg diffraction angle.

4. The imaging system of claim 1, further comprising an optical fiber and a laser collimator disposed between the laser emitting device and the acousto-optic crystal, and the laser emitting device is connected to the laser collimator through the optical fiber.

5. The imaging system of any one of claims 1-4, further comprising a light homogenizer disposed between the laser emitting device and the acousto-optic crystal and a light transmissive component with a window disposed between the light homogenizer and the acousto-optic crystal;

6. The imaging system of claim 5, wherein the window is rectangular.

7. The imaging system of claim 5, further comprising a beam expanding unit disposed between the laser emitting device and the dodging device.

8. The imaging system of claim 7, wherein the beam expanding unit comprises a first lens and a second lens with different focal lengths and diameters, and the first lens and the second lens are sequentially arranged between the laser emitting device and the dodging device.

9. The imaging system of claim 1, further comprising a first polarizer disposed between the laser emitting device and the acousto-optic crystal and a second polarizer disposed between the acousto-optic crystal and the optical imaging device.

10. The imaging system of claim 1, further comprising a focusing lens disposed between the acousto-optic crystal and the optical imaging device.